Various estimation apparatus for estimating the roll angle of a vehicle such as motorcycle have been proposed. For example, the direction of the lighting unit may be controlled based on a roll angle estimated by an estimation apparatus to direct light in an appropriate direction from the lighting unit regardless of the inclination of the vehicle.
Patent Document 1 describes a vehicle-attitude estimation apparatus that estimates the roll angle and pitch angle based on detected values of the front/rear acceleration, lateral acceleration, top/bottom acceleration, yaw acceleration, and roll angular velocity of the vehicle, an estimated value of the front/rear vehicle-body velocity, and an estimated value of the pitch angular velocity.